Short answer. Together. Article 849 says that when a testator calls a person and his children to the succession, they are all deemed instituted simultaneously and not successively. Your uncle does not take first with the children inheriting only after him — he and his children are co-heirs from the start, each in his own right.
What the law says
When the testator calls to the succession a person and his children they are all deemed to have been instituted simultaneously and not successively.
Civil Code, Article 849 — A Person and His Children. Read the full provision →
What Article 849 settles
Article 849 provides that when the testator calls to the succession a person and his children they are all deemed to have been instituted simultaneously and not successively. The phrase 'and his children' is ambiguous on its face. It could mean the named person inherits, and his children take only afterwards, as his successors — or it could mean the person and the children all inherit at once, side by side. The article picks the second and makes it the rule: simultaneous institution, everyone a present heir, not a chain in which one waits for another to die.
Simultaneous, not successive — why it matters
The distinction is not academic. If the institution were successive, the named person would take the whole and the children only what was left when he died — a kind of built-in substitution, with the children's rights postponed and contingent. Because Article 849 makes it simultaneous instead, the children are heirs in their own right from the opening of the succession, not mere expectants waiting on their father. They do not inherit through him or after him; they inherit with him. That protects the children from having their shares defeated by whatever the father might do with property he would otherwise have held first.
How the property is divided
Being instituted simultaneously, the person and the children share the gift as co-heirs. In the absence of stated proportions, that points to an equal division per head — the named person counting as one heir and each child as one heir, all on the same footing. So a gift to 'my uncle and his children', where the uncle has three children, is shared among four co-heirs. The named person is not elevated above the children by being mentioned first; the article's whole point is that they stand together. Any different split has to come from the testator saying so expressly in the will.
What to check in your situation
Start by identifying the children meant — ordinarily those living when the succession opens — and count them together with the named person as co-heirs of equal standing. Look through the will for any words that fix particular shares or that genuinely postpone the children's interest, since express terms control over the default. Do not accept an assertion that the uncle 'inherits first' and the children only later; that is precisely the successive reading Article 849 rejects. If the property has already been transferred to the named person alone, the children's simultaneous right is the ground on which that can be questioned.